Sealant material

ABSTRACT

A sealant for the remedial sealing of self-sealing coke oven doors, or ordinary coke oven doors sealed with a conventional lute, or for sealing spigot joints in off-gas pipe lines in coke oven installations comprises a mixture of from 25 to 45% of a latex, (preferably a PVA-based latex) from 10 to 25% water, from 25 to 45% of a particulate filler (preferably a talc) and from 5 to 15% of an inorganic fiber (preferably an asbestos fiber). At least 40% of the fiber should pass through a British standard 100-mesh sieve. 
     The sealant may vary from a flowable to a putty or paste-like consistency and may be applied by spraying or trowelling as appropriate. If the inorganic fiber is not an asbestos the sealant may also include a proportion of a water soluble thickener to enhance the compatibility of the mixture.

This is a division of application Ser. No. 109,023 filed Jan. 2, 1980,which was a continuation of application Ser. No. 777,055 filed Mar. 14,1977.

This invention concerns a sealant especially, but not exclusively,useful for sealing coke oven doors. It is envisaged as being applicablefor the remedial sealing of worn self-sealing coke oven doors orordinary doors which have been sealed with a lute, and for sealingspigot joints and the like in off-gas pipelines from coke ovens.

Coke ovens can be severely damaged if, during operation, air is allowedto enter them. To prevent this, the pressure inside the coke oven andthe off-gas pipelines is maintained higher than atmospheric pressure byup to 7 mm, typically 1 to 4 mm, water gauge. Thus the gas inside thesystem can escape to the atmosphere, causing pollution and increasingthe danger of fires outside the coke oven.

In order to reduce the amount of pollution the doors of the coke ovensof the ordinary type may be sealed around their edges with aconventional clay-based lute, or a foamable lute as described in ourco-pending U.S. Pat. No. 4,111,709, or the doors are of the self-sealingtype. These measures substantially reduce the escape of polluting gases.

However, lutes dry out during the operation of the coke oven, and thelute shrinks, cracks and separates from the metal of the door and/orframe even though this problem is significantly lessened with thefoamable lute. Also gaps form between the self-sealing doors and theirframes because the doors, after a number of operational cycles, maybecome warped or because tar build-up on the doors may prevent propersealing. Polluting gases can escape through the cracks and gaps, and canalso escape from ill-fitting spigot joints in the off-gas pipelines ofcoke ovens.

It is an aim of the present invention to provide a sealant which can beapplied easily to cracks, gaps and spigot joints in a coke oven systemto prevent the escape of polluting gases to the atmosphere. The sealantshould be effective as a sealant, even though it may become brittle, atleast for the time necessary to complete the carbonisation cycle of thecoke oven at a temperature of up to 200° C., which is the maximumtemperature the sealant normally experiences in such uses during thecycle. The average time of a cycle is about 16 hours. The sealant shouldbe effective as a sealant and should remain flexible for much longer atabout 80° C., which is the average temperature of a spigot joint after awater spray in the off-gas pipeline. The flexibility is necessary toallow for movement of the joints during the operation of the coke ovenover a long period.

All percentages hereinafter are by weight of the total compositionunless otherwise stated.

The sealant according to the invention comprises from 25 to 55% of alatex, from 10 to 25% water, from 25 to 45% of a particulate filler, andfrom 5 to 15% of an inorganic fibre, at least 40% of which fibre willpass through a British Standard 100-mesh sieve.

The latex should preferably contain about 50% solids and have a pH valueof not less than 4.5. Especially suitable are latexes based onpoly-vinyl acetate (PVA).

Preferably, the particulate filler is finer than 200 mesh (BritishStandard), and is conveniently a talc.

The inorganic fibre may be mineral wool, or glass, ceramic or asbestosfibres, and preferably is an asbestos of the amostie variety.

Ceramic fibres may have different wetting properties from those ofasbestos fibres. Therefore if ceramic fibres are used in the sealantcomposition it may be necessary to incorporate therein a water solublethickening agent, such as sodium carboxymethyl cellulose, in an amountsufficient to ensure that all the components of the composition areintimately mixed with one another. The exact amount of thickening agentnecessary will depend on the properties of the ceramic fibre used, butis usually about 2% by weight of the total water content of thecomposition.

There may also be included in the sealant as described above from 0.5 to5%, preferably less than 1%, of a blowing agent which decomposes to giveoff gas in the temperature range from 140° to 220° C. The inclusion of ablowing agent will tend to counteract any shrinkage of the sealantduring the cycle of the coke oven.

The blowing agent may be a mixture of two or more blowing agents. Aparticularly suitable blowing agent is a mixture of "Genitron" OB,blowing in the temperature range from 140° to 160° C., and "Genitron"AC2, blowing in the range from 190° to 220° C. These blowing agents maybe admixed in amounts by weight of from 3:1 to 1:3, but conveniently a1:1 ratio by weight is used. "Genitron" blowing agents are marketed byFisons Industrial Chemicals, Cambridge.

The composition of the sealant can be varied within the defined limitsto give varying flow properties, the quantity of fibre being especiallyimportant in this respect. A paste-like sealant which can be applied bya trowel is obtained by using relatively low amounts of water andrelatively high amounts of fibre. Paste-like sealants are particularlyuseful for sealing spigot joints and cracks appearing in dried lutes onordinary coke oven doors.

A flowable sealant, which can be applied by an applicator gun, is givenby using relatively high amounts of water and relatively low-amounts offibre. With flowable sealants the present invention the gun of does notrequire a piston in the reservoir, but the sealant can be supplied underthe action of air pressure. Flowable sealants are particularly usefulfor sealing gaps around self-sealing coke oven doors.

Accordingly, this invention also provides a method of sealing a crack orgap through which gases may escape, comprising applying to said crack orgap a sealant as described above.

The sealant and method of the present invention could also be used inother systems where escaping gases produce pollution, for instancearound furnaces and piping in industrial chemical complexes or aroundpottery kilns etc.

By way of example only, three formulations of sealant according to theinvention are given below.

    ______________________________________                                                  Sealant 1.                                                                             Sealant 2. Sealant 3.                                      ______________________________________                                        PVA-latex   35%        47%        35%                                         Water       15%        20%        15%                                         Talc        40%        26%        39%                                         Asbestos Fibre                                                                            10%         7%        10%                                         Blowing agent                                                                             --         --          1%                                         ______________________________________                                    

In these examples the PVA-latex used is Vinyl Products Ltd. Grade 99830PVA-latex, the talc is English China Clay Co. grade S2 talc, theasbestos is Cape Asbestos Fibres Ltd. Amosite Grade S44 or Grade S6605,and the blowing agent is a 1:1 mixture by weight of "Genitron" OB and"Genitron" AC2.

The sealants are normally prepared by diluting the PVA-latex with waterto give the appropriate proportions of latex and water, mixing the talc(and,if included, the blowing agent) into the PVA-latex/water mixture,and finally mixing in the asbestos fibre. The addition of the asbestosfibre causes the mixture to become more viscous and so care must betaken to ensure that complete mixing is achieved.

Sealants 1 and 3 are particularly suitable for application by trowel,and may be used to seal cracks in conventional lutes around ordinarycoke ovendoors and to seal spigot joints. They are of a kneadable orputty-like consistency. They are flexible and remain so for aconsiderable time at about 80° C.

Sealant 2 is particularly suitable for application by spray gun, and maybeused to seal gaps around worn self-sealing coke oven doors.

The sealants according to the invention and illustrated above retaintheir sealing action around coke oven doors for at least the duration ofone operational cycle of the coke oven and seal spigot joints for atleast sixmonths during the normal operation of the coke ovens, and areeffective in reducing the amount of pollution caused by the operation ofcoke ovens.

What is claimed is:
 1. The sealant composition comprising a coke oven door sealant for coke oven doors and joints and like installations which coke oven doors sealant remains effective as a sealant to prevent gas leakage from coke oven doors and joints and the like at temperatures up to about 200° C., the coke oven door sealant having from about 25 to 55% polyvinyl acetate-based latex, said latex having a solids content of about 50% and having a pH of not less than about 4.5, the sealant having from about 10 to 25% water, and having from about 25 to 45% of a particulate filler, which is finer than 200 mesh British Standard, the coke oven door sealant having from about 5 to 15% of an inorganic fiber, at least about 40% of which fiber will pass through a 100 mesh British Standard sieve, the sealant composition further comprising from about 0.5 to about 5% of a blowing agent which decomposes in the temperature range from about 140° to 225° C. to give off a gas, the blowing agent tending to counteract any shrinkage tendency of the coke oven door sealant being effective as a sealant against gas leakage during a cycle of use, with any shrinkage tendency of the coke oven door sealant being counteracted by the blowing agent, for several hours at temperatures of up to about 200° C. and the coke oven door sealant being effective as a gas sealant and remaining flexible at temperatures of up to about 80° C. for several months.
 2. A sealant composition according to claim 1, which contains less than 1% of the blowing agent.
 3. A sealant composition according to claim 1, in which the blowing agent comprises a mixture of a first blowing agent in the range of about 140° to 160° C. and a second blowing agent blowing in the range of about 190° to 220° C.
 4. A sealant composition according to claim 3, in which the first and second blowing agents are mixed in a ratio by weight of from about 3:1 to about 1:3 respectively.
 5. A sealant according to claim 3, in which the first and second blowing agents are mixed in a ratio of about 1:1.
 6. A sealant composition according to claim 1, in which the particulate filler is a talc.
 7. A sealant composition according to claim 1, in which the fiber is selected from a group of fibers consisting of asbestos fiber and ceramic fiber. 